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The differences are quite hazy. The concensus is that the 906 heads have a hardened exhaust seat that appears to have a 1 angle valve job done on it that hinders flow. Thus the 906 heads have a slight stigma about them. In practice, I think you should get a valve job done on used heads anyway and the problem is easily rectified.
Here's a shot of my old junk 906 heads that DANS87GTA RIPPED ME OFF with where you can see the hardened exhaust valve seat:
Sorry, Im still angry at the punk for ripping me off on them...
LT1s still use a dizzy-type shaft as an oil pump drive...Right? So I think a LT1 cam would swap right in, no problem. At least, I've never heard of anyone having to get a gear pressed onto the LT1 cams. Just the issue of the nose pin being different, for the Opticrap, which is easily swapped out for the right pin.
062 didn't have hardened exhaust seat but a 3 angle valve job?
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How did that happen to your heads?
He and his partner in crime ( shagwell ) ported 3 exhaust ports in the heads through to the water jacket, had them brazed back up and sold them to me as perfectly good heads. As soon as the car was run it just pumped out water and steam and set back my build by about 3 months and $600 for a set of junk heads.
But either way, it's a bit OT so I'll let your thead continue.
Ok, I just checked Autozone and Advance and they are stating the same thing as Summit did. 88-92 Camaros and Firebirds use a reverse rotation WP and 96-2000 Vortec V8 use a standard rotation WP.
Is this because of the different Acc.-Serp setups on 88-92 Camaros and Firebirds compared to a 96-2000 truck setups?
I have a 97 Tahoe with a 350 Vortec. It is still a reverse rotation pump.
The "reverse-rotation" is because of the serpentine belt system. Think about it for a second. Which pulleys on a serpentine system drive off the backside of the belt? The water pump, the tensioner pulley, and idler pulleys, are the ones driving on the backside of the belt on most serps. The easy way to remember it, is the belt wraps around the pulley in the opposite direction to drive of the back. Thus the pulley spins in the opposite direction.
It is not easily possible to mix them up. The pulley mount holes are drilled/tapped differently. Don't ask how I know that. It's one of those things one is embarassed to have done.
L31 cam specs are not THAT far off the 92 TPI specs, but theheads themselves flow WAY better...plus the seqential firing order of the inectors equals better mpg. If you use the L31 ECM, distributor & wiring.
96 L31 Camshaft Profile
Intake: .275 X 1.5 = .412
Exhaust: .281 X 1.5 = .423
Lobe Separation 111 Degrees
You can use an L31 ecm to run a TPI?
Last edited by InfernalVortex; 07-06-2008 at 03:53 AM.
SUBSCRIBED! Thanks, been looking for a thread like this. My Camaro needs a valve job. And I have a Vortec 5.7 out of a 99 Express laying around that I wanna convert to TPI and drop it right in.
__________________ Car - 1984 Toyota Supra P-Type - 5MGE, Auto(for now), 4:10 LSD,
1988 Camaro IROC-Z : TPI 350 .040 over/700R4/ Edlebrock Headers, Custom 3" Catback SOLD
yeah you spend your time porting the piss out of those 081 heads and he can bolt up his vortecs and put down the same if not more without touching the heads... and if he decideds to clean them up a bit even better... there is a reason they say the vortec head is the best gen1 production head ever...
oh yeah try and find a difference in a "vortec block" and a gen I block
The LT4 cam is an awesome cam upgrade for the L31 Vortec engine. It has more lift, more duration, and a wider LSA. It has more area under the curve as well. It is a very smooth idling camshaft that likes to rev. The LT4 cam fits in with vortec heads very nicely, with LT4 .050" offset retainers, shims, and a good set of valve springs. I have one in my otherwise stock L31 Vortec longblock in my Fullsize G1500 Conversion van. With the 2,000 rpm converter and Tri-Y headers, it came to life all over the powerband. It pulls hard from just off-idle all the way to the 5,600 rpm fuel shut-off on the stock tune.
The LT4 cam is an awesome cam upgrade for the L31 Vortec engine. It has more lift, more duration, and a wider LSA. It has more area under the curve as well. It is a very smooth idling camshaft that likes to rev. The LT4 cam fits in with vortec heads very nicely, with LT4 .050" offset retainers, shims, and a good set of valve springs. I have one in my otherwise stock L31 Vortec longblock in my Fullsize G1500 Conversion van. With the 2,000 rpm converter and Tri-Y headers, it came to life all over the powerband. It pulls hard from just off-idle all the way to the 5,600 rpm fuel shut-off on the stock tune.
What if you took out your LT4 cam and replaced with a 90-92 L98 stock cam in your G1500?
What difference would you see?
Again, I'm weak on cams and the L31 stock cam will not be used.
Hey everyone. Just registered. Glad to find people that know a little bit about the Votec 350/5700/L31... Whatever you want to call it. I have a 96 L31 in my 77 Camaro.
I'm glad to find out that the cam is a roller cam, that makes it a lot easier to swap it out without having to get a "retro-fit" roller cam.
So I keep hearing that the Vortec heads are awesome and they'll sell really well any everything. I understand that they outflow other OE heads and everything, but why should I keep them over buying a new set of something like Edelbrock E-Tec 170cc heads? Obviously with the E-Tec 200cc heads there's a bigger intake runner which makes it clear why that head would outperform the stock head. But would the 170cc E-Tecs actually outperform the stock heads with the stock cam?
And just how much will the OE Vortec heads go for?
Also, how many horses will the rotating assembly take before having to change that out? It's probably a cast crank and pistons?
Lastly, I read that the max lift on the stock head was like .490. That's just because of the valve stem length right? How far till you reach the piston?
I guess what I don't get is, if I put an E-Tec head on my L31 and the max valve lift is .575 and the cumbustion chambers are still 64cc, There must still be room with the stock head to change out the vavles and springs for a higher lift then, right?
I understand that they outflow other OE heads and everything, but why should I keep them over buying a new set of something like Edelbrock E-Tec 170cc heads?
People go vortec because they are cheap. Plain and simple. Of all the OEM heads they flow the best
Setting cost aside and going aftermarket heads, the usually cant compare without significant porting, and even then a ported aftermarket usually trumps them again
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But would the 170cc E-Tecs actually outperform the stock heads with the stock cam?
Compare flow charts. Most likely, yes it will
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And just how much will the OE Vortec heads go for?
Check the classifieds and ebay there is no set value
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max lift on the stock head was like .490. That's just because of the valve stem length right?
Max lift is based on the stock valve springs. They are rated for the stock cam, no more. The issue with upgrading springs is clearance around the valve guides. While a minor job for a machine shop, its an unforeseen cost to the cheap hotrodder
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if I put an E-Tec head on my L31 and the max valve lift is .575 and the cumbustion chambers are still 64cc, There must still be room with the stock head to change out the vavles and springs for a higher lift then, right?
Match your cam to your head flow and intake design, match the valve springs to the cam
Max lift is based on the stock valve springs. They are rated for the stock cam, no more. The issue with upgrading springs is clearance around the valve guides. While a minor job for a machine shop, its an unforeseen cost to the cheap hotrodder
The problem is with spring bind, which can now be overcome at home, with zero machine work done.
There is now a conical spring set available to replace the stock ones. Which like any other spring set.....You can replace the Vortec ones at home, with no more than pulling the rockers off.
Upping the calve lift ability over stock. Simple upgrade.
Or you can buy brand new Vortec heads that already have the spring replacement done for you.
If I install the L98 cam I believe I won't have to do as much prom re-programming.
just leave the vortec cam in there, it is almost identical, and not really worth the effort to take it apart, the vortec cam is a little better aswell. it will run just fine on the stock prom
.490 is the max you run on a stock Vortec head. But it's fairly easy (for a machine shop) to up the lift capability.
